The significance of residual disease after external irradiation of squamous-cell carcinoma of the oropharynx.

366 patients with squamous-cell carcinoma of the oropharynx treated by external irradiation were studied to see whether residual disease at the end of treatment influences control. The frequency of recurrence was found to be significantly greater when residual disease was present. When the total dose was determined by the degree of regression of the primary lesion during treatment rather than the initial tumor volume, recurrence was significantly more frequent. Forcing the dose beyond a level suitable for the original volume of disease failed to prevent recurrence in patients with residual disease, most likely due to the hypoxic state of the remaining tumor cells.